Completed Negative Magic tool as a plugin (except sound).

Created Mirror and Flip Magic tools as plugins (except sound); hooks
added to Magic plugin API to allow starter and starter-undo mirror/flip.
Created Fade and Darken Magic tools as plugins.
Moved magic tool sounds to 'magic'.
Added flip and mirror icons to main Tux Paint UI (used to share magic tools')
Created 'tp-magic-config.sh' to get CFLAGS for compiling magic tool plugins.
Improved magic tool plugin API.
Committed some documentation on magic tool plugin API.

docs/CHANGES.txt

@@ -9,13 +9,31 @@ http://www.tuxpaint.org/
 $Id$
 
 
-2007.July.4 (0.9.18)
+2007.July.5 (0.9.18)
   * System-Related Improvements:
     ----------------------------
-    * Adding an API for developing Magic tools as plug-ins.
-      (e.g., '.so' shared objects under Linux)
+    * Added an API for developing Magic tools as plug-ins.
+      ('.so' shared objects under Linux, '.dll' libraries under Windows, etc.)
+      Plugins must provide a number of functions that Tux Paint calls,
+      and Tux Paint provides a structure ("magic_api") that includes info.
+      (e.g., the running Tux Paint's version number) and pointers to
+      useful functions (e.g., getpixel(), putpixel(), etc.)
 
-    * Ported (most of) 'Negative' magic tool to Magic tool plug-in system.
+    * Magic plugin development can be done outside of Tux Paint base
+      source-code by using new "tp-magic-config" shell script to query
+      for C compiler flags, which points to where "tp_magic_api.h" header
+      file is installed.
+
+    * Magic plugin development docs created.  On Linux/Unix, installed into
+      /usr/[local/]share/docs/tuxpaint-dev/ by default.
+
+    * Ported existing magic tools to the new Magic tool plug-in system:
+      - Negative
+      - Mirror
+      - Flip
+      - Fade
+      - Darken
+      [[ FIXME: Do the rest ]]
 
   * New Translations:
     -----------------